In general, a system that transmits electric power in a non-contact manner is constituted of a power transmission device and a power reception device. The power transmission device comprises a control circuit and a power transmission antenna. The power transmission device, by using the control circuit and the power transmission antenna, communicates with the power reception device and transmits AC power to the power reception device. The control circuit controls a communication signal (hereafter, simply referred to as “signal”) when the power transmission device communicates with the power reception device. Moreover, the control circuit controls electric power transmission of the power transmission device. The power reception device comprises a power reception antenna, a communication section, a rectifier circuit and a DC-DC converter. Moreover, the power reception device is connected with a load. The communication section of the power reception device processes the signal which is sent from the power transmission device. The rectifier circuit converts, into direct current voltage, the AC power received from the power transmission device, and the direct current voltage is output. The direct current voltage output from the rectifier circuit is supplied to the load via the DC-DC converter. The power transmission device and the power reception device communicates with each other when the electric power is transmitted as described above. The communication and the electric power transmission can be performed in a time sharing manner by using the pair of the power transmission antenna and the power reception antenna. In this case, the power reception device uses the single power reception antenna for both the communication and the electric power reception.
For example, Patent Document 1 discloses a power reception device which uses a single power reception antenna to communicate and to receive electric power.
The power reception device of Patent Document 1 comprises a secondary side antenna (power reception antenna), an RFID (communication section) including a first rectifier circuit, a second rectifier circuit, a functioning section (load) connected to the second rectifier circuit, and a bypass circuit. The first rectifier circuit and the second rectifier circuit are connected in series to the secondary side antenna. The bypass circuit is connected in parallel to the first rectifier circuit. The bypass circuit adjusts ratio between electric current flown in the first rectifier circuit and electric current flown in the second rectifier circuit. Accordingly, large electric power can be supplied to the functioning section without being limited because of endurable voltage of the RFID. In other words, even when the large electric power is supplied to the functioning section, the RFID can be protected.